Endolymphatic mass in a patient with undiagnosed multiple myeloma

A 68-year-old Caucasian male with a history of coronary artery disease, a recent clavicular fracture, and vertigo sought emergency evaluation for recent episodes of vertiginous attacks with imbalance. Initial episodes of vertigo were well managed with triamterene and hydrochlorothiazide (HCTZ) until several weeks after presentation. He noted that the attacks were worse with position change and nearly caused him to fall on multiple occasions. He also acknowledged hyperacusis in the left ear. On physical examination, he had a positive Romberg’s sign and leaned to the left with tandem gait. His hearing with the fi nger rub test was louder on the left than the right. An MRI brain with and without contrast demonstrated an enhancing mass in the left temporal bone in the area of the endolymphatic sac, which extended inferiorly towards the jugular foramen (Figure 1).

left iliac bone ( Figure 2). Percutaneous biopsy of the soft tissue mass revealed a CD138-positive, kappa light chain-restricted plasma cell neoplasm, and was negative for pankeratin, CD20, and lambda light chain, leading subsequently to a diagnosis of multiple myeloma (MM) based on bone marrow biopsy. Intracranial extension of the MM lesion from the skull base and involvement of the endolymphatic sac was ultimately responsible for his presenting symptoms. No immediate surgical intervention was recommended and the patient was referred to Oncology for second opinion. In collaboration with Oncology, a conservative approach was agreed to be the best option..

Discussion
Multiple myeloma (MM) is a neoplastic disorder formed by monoclonal proliferation of immunoglobulin-secreting plasma cells. There are often neurological sequelae in patients with MM such as spinal cord compression, spinal radiculopathies, peripheral neuropathies, and cranial nerve palsies; however, direct intracranial symptomatology is rare [1,2]. This patient did not initially present with symptoms classical for MM, but instead secondary to symptoms attributable to his intracranial metastasis. The symptomatology and location of his lesion suggested an endolymphatic sac tumor, and the radiographic characteristics were comparable to that of true endolymphatic sac tumors ( Figure 3).
Concern for metastatic disease was felt to be unlikely on initial evaluation due to focal neurological fi ndings and lack of bony metastasis clearly identifi ed on initial imaging. Glomus tumors typically present with "salt and pepper" distribution on MRI with a low T1 signal and intense enhancement following contrast. Cholesteatomas similarly have low T1 signals, but no enhancement with contrast, while cholesterol granulomas display T1 hyperintensity with no post-contrast enhancement, or only peripheral rim-enhancement. These alternatives were unlikely given the location and pattern of enhancement seen in our patient ( Figure 1). Subsequent imaging of his viscera confi rmed the diagnosis of metastasis.
In cases of intracranial MM, the median interval from MM diagnosis to CNS involvement is about 13 months. 3 Given this delay, neurological symptoms as an initial presentation of MM are uncommon and have only been documented in limited numbers [3][4][5][6][7][8][9][10][11]. CNS involvement of MM signifi cantly decreases overall survival; however, whether or not an initial neurological presentation of MM affects lifespan is unknown [ 3,5]. Clinical course of these rare cases varies widely depending on disease stage and treatment modalities, and have insuffi cient followup to draw any concrete conclusions. Hyperviscosity syndrome secondary to an elevated paraprotein level occasionally presents with vertigo, imbalance, and hearing changes, but our patient did not exhibit other classical signs, such as bleeding diatheses or visual disturbances [1,12]. To our knowledge, this is the fi rst report of MM initially presenting with vestibular dysfunction due to isolated intracranial MM lesions.
Intracranial plasma cell neoplasms typically arise by direct extension from cranial bone lesions or leptomeningeal spread, but may also rarely present as an intraaxial brain lesion without osseous or dural contacts [3]. Intracranial plasmacytomas are very radiosensitive, and optimal treatment often involves total surgical resection followed by post-operative radiotherapy [3,[6][7][8]10,13,14]. In cases of plasmacytomas involving the skull base, complete resection may be impossible given anatomic restrictions, and should be treated with subtotal resection and irradiation, or irradiation alone.3 , 6 The treatment in such cases is controversial but usually involves common myeloma therapies  with immunomodulatory drugs, proteasome inhibitors, and consolidation with a bone marrow transplant are favored over surgical resection. In some cases, chemotherapy regimens were also used [3,5,6,8,10,11,14]. Median life expectancy of patients with MM at the skull base is 3 years, but prognosis is improved following high-dose chemotherapy and stem cell transplantation [3,5,7,10,11]. There are very few reports of surgical resection in cases of intracranial MM, most of which were always performed prior to an established diagnosis of MM and followed by chemotherapy, radiation therapy, and/or stem cell transplantation [4,6,14]. Review of the literature identifi ed two cases of intracranial MM treated with only surgery: both patients had craniotomies for symptomatic parietal lesions -one had a history of MM in remission and passed 1 month post-op before further treatment could be pursued, the other was diagnosed with MM post-opearatively, but refused further treatment and passed 6 months later [14]. If the lesion in our patient were to be treated with surgical resection alone, as is recommended with endolymphatic sac tumors due to the controversial role of radiation or chemotherapy, our patient would likely rapidly deteriorate due to the diffuse nature of his disease [15][16][17].

Conclusions
Multiple Myeloma represents one of the "great imitators" of modern medicine. While rare, skull base lesions may represent a number of primary or secondary malignancies.
Thorough consideration of the possibility of metastasis is advisable even in circumstances involving pathognomonic radiographic fi ndings. Presentation with neurological fi ndings is uncommon in MM, and suggests an unfortunate prognosis when coupled with diffuse systemic disease.